The present invention relates to a process for preparing at least one monocyclic ketone having from 4 to 20 carbon atoms by reacting a mixture G1 comprising at least one monocyclic olefin having from 4 to 20 carbon atoms with a mixture G2 comprising at least dinitrogen monoxide (N2O), wherein said reaction is performed adiabatically.
Processes for preparing cyclopentanone are known in principle from the prior art. It is likewise known that cyclopentanone can be obtained by reacting cyclopentene with dinitrogen monoxide. The preparation of cyclopentanone by oxidation of cyclopentene with dinitrogen monoxide is a very selective reaction which is strongly exothermic.
For instance, GB 649,680 discloses the reaction of alkenes, for example cyclohexene, with dinitrogen monoxide in order to obtain the corresponding cyclic ketones, for example cyclohexanone. The reaction is performed at a temperature of from 200 to 300° C. and a pressure of from 100 to 500 bar in the liquid phase. The document cited does not disclose that cyclic olefins are reacted with dinitrogen monoxide under adiabatic conditions.
F. S. Bridson-Jones et al. describe, in J. Chem. Soc., p. 2999-3008 (1951), the reaction of olefins with dinitrogen monoxide, which converts, for example, cyclohexene to cyclohexanone. The process according to this document is performed at a temperature of, for example, 300° C. and a pressure of 500 bar in an autoclave. F. S. Bridson-Jones et al. do not disclose that cyclic olefins can be reacted with dinitrogen monoxide under adiabatic conditions.
The synthesis of carbonyl compounds from alkenes with dinitrogen monoxide is also described in various international patent applications. For instance, WO 03/078370 discloses a process for preparing carbonyl compounds from aliphatic alkenes with dinitrogen monoxide. The reaction is performed at temperatures in the range from 20 to 350° C. and pressures from 0.01 to 100 bar. WO 03/078374 discloses a corresponding process for preparing cyclohexanone. According to WO 03/078372, cyclic ketones having from 4 to 5 carbon atoms are prepared. According to WO 03/078375, cyclic ketones are prepared under these process conditions from cyclic alkenes having from 7 to 20 carbon atoms. WO 03/078371 discloses a process for preparing substituted ketones from substituted alkenes. WO 04/000777 discloses a process for reacting di- and polyalkenes with dinitrogen monoxide to give the corresponding carbonyl compounds. No adiabatic process for preparing cyclic ketones from the corresponding cyclic olefins is disclosed in the international applications cited.
U.S. Pat. No. 4,806,692 discloses a process for preparing oxygen-comprising organic compounds from olefins; more particularly, the oxidation of cyclic olefins under mild conditions is disclosed, in order to obtain corresponding cyclic ketones. According to U.S. Pat. No. 4,806,692, such an oxidation is effected in the presence of palladium catalysts at a temperature of 80° C. or lower and atmospheric pressure. U.S. Pat. No. 4,806,692 does not disclose a process for preparing cyclic ketones from the corresponding cyclic olefins by reaction with dinitrogen monoxide under adiabatic conditions.
U.S. Pat. No. 7,282,612 B2 discloses a process for preparing monocyclic ketones having 4 or 5 carbon atoms by reacting the corresponding cyclic alkenes having 4 or 5 carbon atoms with dinitrogen monoxide, if appropriate in a mixture with an inert gas at a temperature of from 20 to 300° C. and a dinitrogen monoxide pressure of from 0.01 to 10 bar. No adiabatically performed process is disclosed in U.S. Pat. No. 7,282,612 B2.
RU 2002106986 discloses a process for preparing monocyclic ketones having 4 or 5 carbon atoms by oxidation of cyclobutene or cyclopentene with dinitrogen monoxide, likewise at a dinitrogen monoxide pressure of from 0.01 to 100 bar and a temperature of from 20 to 300° C.
The reaction of monocyclic olefins with dinitrogen monoxide in order to obtain the corresponding ketones is strongly exothermic. In addition, mixtures of dinitrogen monoxide with organic compounds having a high concentration of dinitrogen monoxide pose an explosion risk. It is therefore necessary for a corresponding prior art process to provide complicated and costly apparatus for heat removal from the exothermic reaction. Furthermore, the reactors have to be designed for the high pressures and temperatures.